Intra-arterial blood pump



April 7, 1970 R. T. JONES INTRA-ARTERIAL BLOOD PUMP Filed May 16, 1967 ms w ROBERT T. JONES INVENTOR.

B ATTORNEYS United States Patent 3,504,662 lNTRA-ARTERIAL BLOOD PUlVIP Robert T. Jones, Lexington, Mass., assignor to Avco Corporation, Cincinnati, Ohio, a corporation of Dela- Ware Filed May 16, 1967, Ser. No. 638,867 Int. Cl. A61b 19/00; A61m 1/00 US. Cl. 128-1 13 Claims ABSTRACT OF THE DISCLOSURE As is well known, the systemic circulation is maintained by the action of the left ventricle in pumping blood into the aorta, or main artery. A backflow of blood into the left ventricle is prevented by the aortic valve. During its contraction (systole), the left ventricle works primarily against the elastic compliance of the aorta, raising the pressure in the aorta and distending it. As soon as contraction is complete and the ventricle relaxes, the aortic valve closes and the elastic contraction of the aorta then maintains a continuing flow of blood through the capillaries and other vessels (diastole). In addition to its function as a vessel for carrying blood to various organs, the aorta thus acts as an elastic reservoir storing some of the energy supplied by the heart. In many cases of heart insufiiciency, it is found that the aorta has become relatively stiff and inelastic because of physiological processes, and thus requires excessive pressures from the heart to maintain normal circulation.

Heretofore, extracorporeal mechanical assistance to the systemic circulation has been attempted by veno-arterial pumping, left-heart bypass, diastolic augmentation, intraarterial balloon pumping, and counterpulsation.

Thus, situations are frequently encountered in the treatment of heart patients where the patients heart action is simply not sufficient to supply the patients bodily needs. Frequently, the situation is encountered that while the diastolic action of the heart will bring a volume of blood into the left ventricle of the heart suflicient to supply bodily needs, this ventricle will not fully empty into the aorta. Or, should the ventricle fill the aorta with arterial blood, the systolic action of the heart is not thereafter suflicient in itself to completely discharge the blood content of the aorta into the arterial tree. Blood backs up, stagnates, and seriously impairs bodily function. Conventionally, Weakness in heart action is termed heart failure.

From the foregoing, it will be understood that any practical auxiliary blood pump which will assist the natural heart action in some simple, reliable and predictable manner may be expected to receive recognition and acceptance within the medical field and as well, to subserve a strongly practical function. That the problem is diflicult, however, is apparent simply upon considering that, despite long-felt and very prominent need for such external assistance, and desipte the substantial thought, study and work which have been devoted over the years to this overlying roblem, no really practical solution has as yet been evolved, either as a method of lOng term treatment or as a physical embodiment of heart-assisting means.

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For one reason or another, therefore, the many proposals heretofore propounded by the medical researchers have fallen short of minimum requirements, thereby failing' in recognition and acceptance within the healing arts. Either they have proved too dfficult, delicate and/ or uncertan to maintain in reliable operation, or impractical in fulfilling minimum requirements of either proper relation ship' with natural heart action or volumetric response to minimum standards. Other proposals and/ or related equipment have failed to respond to minimum standards of adjustability to meet adequately the requirements of the cardiac specialist.

An object of the invention, therefore, is to recognize in substantial measure or even to avoid the many defects and disadvantages of prior art blood pumps and in so doing to produce an intra-arterial pump capable of fulfilling the requirements of the art, and, for example, for supplementing in manner and to extent required for each individual patient, his natural heart action, which apparatus may be employed simply and directly, utilizing techniques and equipment, respectively, which in themselves are comparatively readily available, reliable and low in cost.

A further object of the invention is to provide an intraarterial balloon pump having generally a peristaltic action.

A still further object is to provide a pneumatic segmerited blood pump the segments of which have different rates of inflation.

A still further object of the invention is to provide a balloon pump wherein expansion of both of its end portions prior to expansion of its center portion is prevented.

The novel features that are considered characteristic of the present invention are set forth in the appended claims; the invention itself, however, both as to its organization and method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in conjunction with the accompanying drawings, in which:

FIGURE 1 is a sectional view of the invention on an enlarged scale with parts broken away;

FIGURE 2 is a sectional side view with parts broken away of a modification of the invention; and

FIGURE 3 is an end view taken on line 3-3 of FIG- URE 1.

One embodiment of an intra-arterial type pump in accordance with the invention is shown in FIGURE 1. Here a flexible gas release tube 10 is disposed within a compliant membrane generally designated by the numeral 11. The gas release tube 10 and/ or the catheter may be conveniently formed of a plastic material inert to bodily fluids such as, for example, polyvinyl chloride. Likewise, the compliant membrane which surrounds tube 10 may be formed of, for example, polyvinyl chloride, polyurethane, latex, or silicon rubber and the like.

Gas release tube 10 is atached to or forms part of a tubev or catheter (not shown) which may be of the order of 2 /2 feet long with an external diameter of inch and internal diameter of 7 inch, i.e., with a thickness of 4, inch. Compliant membrane 11 is conveniently collapsible to a deflated volume of, for example, a few cc.s and when inflated, it may occupy a volume of approximately 3055 cc.s. The diameter of membrane 11 at various points along its length is selected such that in its inflated position it will fit within the aorta. Any of the various materials available for the tubes and compliant membrane exposed to body fluids may be used, the principal requirement being that the material or materials be compatible to the human system and not conducive to clotting.

Directing attention now to compliant membrane 11, as shown in FIGURE 1, it should be noted that it is provided with annular restrictions 12 and 13 to contact the gas release tube 10 at spaced intervals 14 and 15 to define a plurality of (in this case three) fluid retaining compartments 16, 17 and 18. Thus, membrane 11 is attached at its extreme ends 21 and 22 as by bonding to the gas release tube 10. Preferably membrane 11 is bonded intermediate its ends as at 14 and 15 when it is desired to completely prevent leakage from one compartment to an adjacent compartment. In such a case, a suitable adhesive may be deposited at the appropriate locations by inserting from the extreme ends of the membrane prior to bonding thereof, the needle of a syringe containing a suitable adhesive. The end of the gas release tube remote from its pressure receiving end 23 is closed with a suitable tapered plug 24 which is preferably bonded to both tube and membrane 11. For a typical insertion via a femoral artery, compartment 18 would be proximate to the heart and compartment 16 would be distal to the heart. For an insertion from an artery in the neck, for example, it would be necessary that the locations of end 23 and plug 24 be reversed.

Attention is now directed to the significant fact that the size or cross sectional area of the openings 25, 26 and 27 in tube 10 at each compartment is different. To be exact, as shown only by way of example in FIGURE l, the size or total cross sectional area of opening 25 in compartment 16 distal to the heart is a minimum, the total cross sectional area of the opening 26 in compartment 17 is maximum, and the total cross sectional area of the opening 27 in the compartment 18 proximal to the heart is intermediate that of openings 25 and 26.

In the conventional technique of intra-arterial balloon pumping, a long narrow balloon is disposed in the aorta where it is rhythmically inflated and deflated in well known manner in synchronism with the beating of the heart. As is well known, such synchronous pumping of the balloon when phased properly with the pumping the natural heart can increase the circulation of blood and can reduce the work load of the heart. Conventionally, the inflation of the balloon is caused by a controlled pulsatile gas flow introduced into the balloon through a long catheter or tube.

For a more thorough discussion of methods and apparatus for actuating a balloon pump, reference is made to US. Patent No. 3,266,487.

The efiectiveness of the conventional balloon pumping technique as set forth, for example, in the above noted US. patent is limited, however, by the fact that the balloon tends to occlude, at least partially, the aorta and hence interposes a not inconsiderable resistance to blood flow along the aorta. This resistance imposed by the balloon acts in opposition to the positive pumping action of the balloon and hence limits its effectiveness.

Inta-arterial balloon pumping techniques are based on the principle that the expansion of the balloon within the artery displaces the blood from the region between the balloon and the inner wall of the artery. However, in methods that use balloon pumps, the flow paths or streamlines originating from the center of the balloon are longest and hence offer greater inertia and resistive impedance to flow. The present invention is biased on this fact and the discovery that under dynamic conditions a greater pressure is accordingly required to expand the center portion of the balloon than is required to expand the end portions. In prior art balloon pumps and techniques for using them, substantially the same inflation pressure appears all along the length of the balloon with the undesirable result that balloons of conventional construction expand first at their ends. The prematurely inflated ends then tend to occlude the aorta and hence offer greater impedance to the displacement of blood away from the center region of the balloon. This unstable and undesirable mode of inflation of prior art pumps was demonstrated in the development of this invention.

In accordance with the invention, the size of the holes in a pump having a plurality of compartments may be pro portioned to permit the order and rate of inflation of the compartments to be controlled. In the embodiment shown in FIGURE 1, the rate of inflation of the compartments (assuming that their volumes do not vary by significant amounts) is controlled by simultaneously supplying different gas pressures to the individual compartments. Thus, by supplying greater inflation pressures initially to the center compartment (because of the tendency of the ends to inflate more quickly) its inflation may be controlled or kept in step with the inflation of the compartments near the ends of the pump. If the center compartment or compartments are inflated slightly in advance of the end compartments, then the pressure diflerences along the pump tend to become equalized.

The rates of inflation and the pressures developed in the different compartments can be most conveniently controlled by providing the gas release tube with orifices having a different size at each compartment. Sequential inflation of the compartments in the direction of blood flow is preferred to produce a peristaltic pumping action in addition to the pure displacement action of the balloon to aid in propelling blood away from the heart. Thus, as shown in FIGURE 1, the orifices admitting gas to the center compartment are larger in diameter than those at the end compartments. Furthermore, by adjustment of the size of the orifices along the length of the pump as by having the minimum size at the distal end and an intermediate size at the proximal end, peristaltic pumping action can be achieved. By peristaltic pumping action is meant that the compartments are sequentially totally inflated, total inflation occurring first in the furthest upstream compartment and last in the furthest downstream compartment. As previously noted, such peristaltic action is desirable to overcome the resistance of the balloon and to provide a suitable distribution of blood along the aorta. Further, during the negative pressure portion of the pumping cycle the proximal compartment of the balloon deflates first making way for the onrush of blood ejected from the heart. Thus, where the compartments are fully inflated sequentially in the direction of blood flow during the positive portion of the pumping cycle, during the negative portion they deflate sequentially in the same direction.

Directing attention now to FIGURE 2, there is shown a modification of the invention wherein the compliant membrane 11a has a conventional outer configuration, i.e., the diameter of the exposed surface of the compliant membrane 11a intermediate its extreme ends 21a and 220: does not change substantially. The membrane 11a may have a substantially constant diameter as shown or be tapered to fit an artery such as shown in FIGURE 1. While a gas release tube 10a, openings 25a, 26a and 27a and plug 24w identical to that shown in FIGURE 1 are provided as and for the purposes discussed in connection with FIGURE 1, inwardly extending annular portions 31 and 32, preferably forming part of the membrane 11a are provided and in conjunction with the extreme ends 21a and 22a of membrane 11a define fluid retaining compartments 16a, 17a and 18a.

Alternately, to facilitate fabrication, the compartments may also be formed by using two membranes, a first membrane bonded at its ends to the gas release tube 10a to define the center compartment 17a and a second membrane surrounding and extending past the ends of the first membrane and also bonded at its ends to the tube as shown in FIGURE 2 to define compartments 16a and 18a. FIGURE 3 shows the pump in its collapsed position as do the broken lines in FIGURE 1.

Inflation, or expansion, then deflation, or collapse, of membrane 11 or 11a is had alternately by way of com pressed gas (such as carbon dioxide or helium) and vacu um applied to the end 23 of tube 11 through action of an external pump. For a more thorough discussion of a suitable external pump system and electronic control system which do not form a part of the invention, reference is made to the aforementioned US. Patent No. 3,266,487. Broadly, for the normal application of an intra-arterial pump in accordance with the present invention, it is disposed within the aorta as by insertion internally of a patient through his femoral artery and up into the aorta. Assuming the timing sequence to be such that the first part of the systolic beat of the heart takes lace, then the heart valve will open from the left ventricle to the aorta. At the same time, membrane 11 is vacuum-deflated so that instead of occupying its maximum volume within the aorta, it suddenly is collapsed to occupy its minimum volume. This provides the required blood displacement volume in the aorta. Such a blood displacement volume may be of about 30 to 50 cc.s. Under pressure not exceeding the diastolic phase of the patients existing heart action, such as, for example, 70 mm. of mercury more or less, blood flows under the action of the patients heart muscle together with moderate ventricular assist of the collapsing membrane, from the left ventricle into the space made available in the aorta, filling the same. The pressure requirement of the heart is at a minimum because instead of calling on the heart to supply the arterial tree, against the back pressure there obtaining, it merely is required to supply blood to the space provided in the aorta by collapse of the membrane 11. Upon completion of such systolic phase, and with the aorta substantially filled, then with the natural heart action the valve closes between the left ventricle and the aorta. The pressure necessary to supply the arterial tree comes from inflation of the membrane, as noted hereinbefore.

It will be evident that the principle of peristaltic pumping by means of inflatable balloons and graduated orifices has other medical applications than that of aortic balloon pumping. In the case of aortic balloon pumping, what is desired is primary synchronous displacement pumping and the peristaltic action is secondary to the main function, being introduced to overcome the resistance of the balloon and to provide a more physiologically correct distribution of blood to the various branching arteries.

The present invention may be used in applications other than aortic balloon pumping such as the perfusion of par ticular organs, the treatment of hydrocephally and the like in which a frankly peristaltic pumping action may be desired. In such applications, a catheter equipped with a plurality of balloons of predetermined volume and having a plurality of orifices of calculated and preferably varying size may be used. The pulsatile gas flow in such cases need not be synchronized with the heart pulse but may, for example, have a much higher frequency.

It will be apparent from the foregoing that the broad application of this invention having now been disclosed, many embodiments, as well as many modifications of those embodiments disclosed, will readily suggest themselves to those skilled in the art. Accordingly, it is intended that the foregoing disclosure be considered as simply illustrative and not as comprising limitations.

What is claimed is:

1. In an intra-arterial type pump for pumping blood and the like, adapted to be connected to a pumping system including pneumatic means for alternately supplying and withdrawing fluid to and from said intra-arterial pump, combination comprising:

(a) a flexible tube, one end of which is closed and the other end of which is adapted to be coupledto said pneumatic means; and

(b) compliant membrane means surrounding said tube and defining therewith a plurality of fluid retaining compartments, said tube having a plurality of openings providing communication between the interior of said tube and each compartment, the volume of said compartments and the cross-sectional area of the openings at each said compartment producing a predetermined and essentially diflferent rate of actuation of each compartment as compared to an adjacent compartment upon operative application of said fluid to said tube.

2. In an intra-arterial type pump for pumping blood and the like, adapted to be connected to a pumping system including pneumatic means for alternately supplying and withdrawing fluid to and from said intra-arterial pump, the combination comprising:

(a) a flexible tube, one end of which is closed and the other end of which is adapted to be coupled to said pneumatic means; and

(b) compliant membrane means surrounding said tube and defining therewith a plurality of fluid retaining compartments, said tube having a plurality of openings providing communication between the interior of said tube and each compartment, the volume of said compartments and the cross-sectional area of the openings at each said compartment producing a peristaltic pumping action when said pump is operatively disposed in an artery and said fluid is operatively coupled to said tube.

3. In an intra-arterial pump for disposition in an artery or the like and having one end proximate to the heart and one end distal to the heart, said pump being adapted to be connected to a heart pumping system including pneumatic means for alternately supplying and withdrawing fluid to and from said intra-arterial pump, the combination comprising:

(a) a flexible tube closed at one end, the other end being adapted to be coupled to said pneumatic means; and

(b) compliant and im erforate membrane means surrounding said tube and defining therewith a plurality of consecutive and discrete pneumatic compartments, the majority of each said compartment having an outer diameter substantially greater than that of said tube, said membrane means sealably enclosing said tube intermediate its ends, said tube being provided with at least one opening at each compartment providing pneumatic communication between the interior of said tube and the interior of each said compartment, the total cross-sectional area of the openings at each compartment being of a size to provide essentially sequential actuation of said compartments when said pump is operatively disposed in an artery and said fluid is operatively coupled to said tube.

4. The combination as defined in claim 3 wherein the volume of each said compartment and the total cross sectronal area of the openings at each said compartment produce, upon operative application of pressure to said tube when disposed in an artery, different rates of expansion of said compartments.

5. The combination as defined in claim 4 wherein the rate of expansion of the compartment proximate to the heart is maximum and the rate of expansion of the balance of said compartments progressively decreases in the direction distal to the heart.

6. The combination as defined in claim 4 where inflation pressure initially is greater in the compartment intermediate the ends of said tube.

7. The combination as defined in claim 3 wherein the volume of the compartments are substantially the same.

8. The combination as defined in claim 3 wherein the exposed surface of said membrane means is composed of a material inert to body fluids, and the total cross sectional area of the openings at each of said compartments are diflerent.

9. The combination as defined in claim 8 wherein the total area of said openings at each of the said compartments is a maximum at a compartment intermediate the ends of said tube.

10. The combination as defined in claim 9 wherein the total area of said openings is a minimum at the compartment distal to the heart and intermediate said maximum and minimum at said compartment proximate to the heart.

11. The combination as defined in claim 3 wherein the total area of openings at each of said compartments progressively varies from a maximum at the compartment 7 proximate to the heart to a minimum at the compartment distal to the heart.

12. The combination as defined in claim 3 wherein said compliant membrane means comprises:

(a) first annular membane means sealably attached at its ends to said tube to define a first compartment intermediate the ends of said tube; and

(b) second annular membrane means surrounding and extending past each end of said first membrane means, the ends of said second membrane means being sealably attached to said tube to effectively define second and third compartments at respectively opposite ends of said first compartment.

13. The combination as defined in claim 12 wherein the diameter of the exposed surface of said compliant membrane means intermediate the ends of said second membrane means does not change substantially.

References Cited UNITED STATES PATENTS 612,724 10/1898 Hamilton 128-344 2,493,326 l/l950 Trinder l28344 X 2,849,001 8/1958 Oddo 128349 2,855,934 10/1958 Daughaday 128-349 3,266,487 8/1966 Watkins et a1 l28-1 3,316,895 5/1967 Lewis l28-2 DALTON L. TRULUCK, Primary Examiner US. Cl. X. R. l28344 

